Motor vehicles – Steering gear – With fluid power assist
Patent
1996-05-30
1998-08-18
DePumpo, Daniel G.
Motor vehicles
Steering gear
With fluid power assist
180417, 91375A, 91450, B62D 506
Patent
active
057947368
DESCRIPTION:
BRIEF SUMMARY
The present invention relates improvements to a fluid control system for a vehicle power assisted steering mechanism.
Power steering mechanisms for automobiles are known which comprise a manually driven steering member, commonly a steering wheel, and a fluid driven driving member, commonly a double acting hydraulic piston and cylinder assembly, which are operatively connected to the steering means, e.g. the road wheels, by which steerage of the vehicle is achieved.
The steering wheel is drivingly connected to a metering valve which is responsive to the load required to move the road wheels so as to meter flow of pressurised fluid to the hydraulic piston and cylinder assembly in order to vary the pressure of fluid supplied for operating the piston.
Such a power steering mechanism is shown for example in our UK patent 1299506.
It is recognized that the degree of power assistance required for rotating the steering wheel varies with speed of the vehicle. A known proposal is to locate a speed responsive metering valve in the flow path for varying the metered pressure of fluid produced by the load responsive metering valve.
However, the power assistance characteristics required differs at high speed to those at low speed and so the metering characteristics of the metering valve driven by the steering wheel are chosen to provide an optimum range of metering values for both high and low speed power assistance. This range of metering values is a compromise between the ideal ranges of metering values for high speed power assistance and for low speed power assistance and is not compensated by the speed responsive metering valve.
It is a general aim of the present invention to provide a fluid control system for a vehicle power steering mechanism which provides improved power assistance response at high and low speeds.
According to one aspect of the present invention there is provided a fluid control system for a vehicle power steering mechanism having a manually driven steering member and a fluid driven driving member operatively connected to steering means of the vehicle by which steerage of the vehicle is achieved, the control system including a first valve for metering pressurised fluid flow to the fluid operated driving member in response to the force required to move the steering means when operating the manually driven steering member, the first valve including at least two independent metering valve means each of which are simultaneously operated by the steering member to meter fluid flow to and/or from the fluid operated driving member at a predefined rate, each metering valve means communicating independently to a drain via a second valve, the second valve being arranged to selectively connect and disconnect at least one of said valve means to the drain in response to vehicle speed.
Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a fluid control system according to one embodiment of the present invention;
FIG. 2 is an axial section through a load responsive metering valve for use in the system of FIG. 1;
FIG. 3 is a more detailed diagram of the system shown in FIG. 1;
FIG. 4 shows a section through IV of FIG. 2.
The fluid control system 10 according to the present invention is hereinafter described incorporated in a power assisted steering mechanism of the type described in our UK patent 1299506. Basically, such a system includes a load responsive metering valve which is manually driven by the driver of the vehicle via a steering wheel. The metering valve includes a valve rotor rotatably housed within a valve sleeve. The opposed faces of the rotor and sleeve have longitudinally extending grooves which cooperate to control flow of fluid through the valve depending upon the relative displacement of the rotor and sleeve.
The steering mechanism includes a rack connected to the steering road wheels of the vehicle and a pinion is mechanically connected to the rotor and sleeve of the load responsive valve. The
REFERENCES:
patent: 4619339 (1986-10-01), Futaba et al.
patent: 4819545 (1989-04-01), Dymond
patent: 5121807 (1992-06-01), Adams
patent: 5152359 (1992-10-01), Emori et al.
patent: 5184693 (1993-02-01), Miller
patent: 5291963 (1994-03-01), Sangret
patent: 5293954 (1994-03-01), Dymond
patent: 5332055 (1994-07-01), Emori et al.
Adwest Engineering Ltd.
DePumpo Daniel G.
LandOfFree
Fluid control system for a vehicle power assisted steering mecha does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluid control system for a vehicle power assisted steering mecha, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid control system for a vehicle power assisted steering mecha will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1107253